Domestic appliance



Nov. 13, 1945. M. E. FRY

DOMESTIC APPLIANCE Filed April 9. 1943 2 Sheets-Sheet 1 PREHEA PREHEAT BAKE BRO.

BAKE

PREI-IEATg BAKE BROIL BAKE OFF

Nov. 13, 1945. FRY 2,388,839

DOMESTIC APPLIANCE Filed April 9, 1943 I 2 Sheets-Sheet 2 P E 6 d 67 Patented Nov. 13, 1945 DOMESTIC APPLIANCE Millard E. Fry, Dayton, Ohio, assignor to General Motors Corporation, Dayton, Chlo, a corporation of Delaware Application April 9, 1943, Serial No. 132,393-

9 Claims. (c1. ale-2o) This invention relates to domestic appliances, and more particularly to electric ranges.

An object of this invention is to provide an electric heating arrangement for ovens which is capable of providing several different cooking conditions with relatively few switch connections.

Another object of this invention is to provide an electric heating arrangement for ovens, which provides a plurality of dliierent cooking conditions with relatively few switches, and in which the polarity of the switch contacts is not reversed when shifting from one cooking condition to another.

Further objects and advantages or the present invention will be apparent from the following de scription, reference being had to the accompany irlg drawings, wherein a preferred form or the present invention is clearly shown.

In the drawings:

Fig. l is a diagrammatic representation of one modification of my invention, in which the elec trio circuit is placed in a preheat position;

Fig. 2 is a view similar to Fig. l, in which the circuit is placed in a bake position;

Fig. 3 is a view similar to Fig. 1, with the cir cult in a broil position;

Fig, l is a view similar to Fig. l, with the elmcuit in the off condition;

Fig. 5 is a diagrammatic representation, in perspective, or" a modified form of ti e invention;

Fig. 6 is a diagrammatic representation, some what in cross section, or the form shown in Fig. 5.

in my improved circuit, an oven is provided with an electrical upper heater ll), and an elec= trlcal lower heater l l, these heaters being placed in the oven with a cooking space between the heaters for baking and broiling articles to be cooked. These heaters are adapted to be conheated and disconnected with two relatively high potential leads L and L1 and a relatively low potential lead N, these leads being adapted to be connected respectively to the lines of a source or power, such as a three-wire single phase source, ln'which there are two relatively high potential lines and a relatively low potential line, the arrangement being such that a high potential is adapted to be provided between the leads L and L1 and a. relatively low potential between either of the leads L and L1 and the low potential, grounded or neutral lead N.

The upper heater I O has a relatively high potential connection l2 between one of its ends 13 and the lead L. It also has an intermediate tap I l. Another relatively high potential connection 55 is provided between the tap M and the lead L1. The other end it of the heater ill has a relatively low potential connection ll with the lead N.

The lower heater ii is provided with a relatively high potential connection it between one of its ends l9 and the lead L. Its other end 2E3 has a relatively high potential connection ll with the lead L1.

Switch means are provided for energizing the heaters to provide a preheat condition, a plu- 23 and it may be operated by a common manual actuator which moves the shaft 25, or other mechanical connection, for operating the switches. This switch means may be of the type which is generally known as a selector switch, which has an actuator or knob 25 to be operated along with a separate thermostat knob, the thermostat being responsive to temperatures in the oven and opening and closing either or both of the leach L and L1. However, as hereinafter more fully described, these switches may be combined with the thermostat structure, so that the entire switch means and thermostat may be operated by a single knob.

In l the knob 2%": is turned to the preheat position. Under these conditions, all of the switches 22, 23 and 2d are closed and all or the high potential connections l2, l5, l3 and 2! are connected with the lines L and L1 and the connection H is connected with the lead N. This places the lower heater H and the section 27 of the upper heater H] across the high potential leads L and L1 and the section 28 of the upper heater ill across the low potential between N and L Preferably the upper heater in is made of a resistance wire of substantially uniform thickness, or resistance, throughout its length, and the tap H is so located intermediate the ends i3 and 18 so that substantially the same amount or current flows through the'sections 21 and 28. For example, if the potential between the leads L and L1 is 235 volts and the potential between Ll.

and N is 117 /2 volts, then the tap i4 is placed so th t section 21 is two-thirds of the length of the heater liland section 28 is one-third of the length of heater i0. Under these conditions the heater to is heated uniformly to the same temperature throughout its length under all of the conditions herein described.

In the bake position, shown in Fig. 2, the lower heater II is connected between the leads L and L1. The upper h'eater I is connected between leads L and N; but is disconnected from the lead L1. Under these conditions the heater II is energized at its full wattage and the heater in is energized at a reduced wattage, because the sectionsjl and 28 are in series between the relatively low potential existing between the leads L and .N. a

In the broil position shown in Fig. 3, the connections l2, l5 and H of the upper heater it are connected to their respective leads L, L1 and N. Under these conditions the upper heater is energized at its full wattage. The connection 2B of the lower heater ii is opened, so that the lower heater H is not energized in the broil position.

In the "01? position shown in Fig. 4 the switches 22, 23 and 24 are opened and the high potential connections l2, I5, l8 and 2! are disconnnected from their respective leads L and L1, so that neither heaters it nor i i can be energized. Since the low potential lead N is ordinarily grounded, the connection I! may remain per- .manently connected to the lead N.

Merely as an example, with a 235 volt, single phase, three-wire circuit, section 21 may have a wattage of 2000-W, section 28 may have l000-W, thus giving heater ill a wattage of 3000, in the preheat position. Heater H may have 2000-W, when in the preheat position. In the bake position heater I0 then will have a wattage substantially equal to 335 watts and heater H a wattage of 2000 watts. In the broil position, heater in has a wattage of 3000W.

In the modification shown in Figs. 1 and 4 inclusive, the switches 22, 23 and 24 diagrammatically show rotary disks actuating reciprocating switches; but it is to be understood that any type of switch may be used. In the form of switch shown, the disks 30, 3| and 32 are illustrated with ridges 33 which come in contact with the swinging or reciprocating arms 34 to open the switch. In this modification arms 34 are spring biased towards the disks, to maintain the switches closed until opened by the action of ridges 33.

Figs. 5 and 6 illustrate a modification in which the thermostat structure is combined with the switches, and the resulting structure is actuated by a single knob. Fig. 5 shows the structure diagrammatically and somewhat in perspective, while Fig. 6 shows it diagrammatically but somewhat in cross section.

In this modification the knob 60 is shown in the o position, and may be rotated counterclockwise from the stop ii past bake positions marked v100, 200, 300, 400, 500 to a broil position where another stop 32 is provided. The numerals 100, etc., are intended to designate degrees of temperature to be maintained in the oven by the adjustment of the thermostat in the bake position. In the broil position, the thermostat is adjusted to approximately 600 F. In order to preheat the oven, the user may rotate the knob 00 counterclockwise to the broil position and then rotate it clockwise to a selected bake position, such as 400. As hereinafter described, such an actuation of the knob 40 causes the switch structure to energize the upper oven heater 43 and the lower oven heater M at their maximum wattage until the oven. reaches the selected temperature (400) at which time the circuit is changed automatically by the thermostat, with the upper heater fit energized at reduced wattage and the lower heater 5% at maximum wattage;

The upper heater 43 is divided into sections 45 and 66. One end 41 of the heater 63 is provided with a connection 48 to the high potential lead L. A high potential connection 49 connects the tap to with the high potential lead L1. The low potential connection 54 connects the end 52 of the heater 63 with the low potential lead N.

A high potential lead 53 connects the end 54 of the heater 04 with the lead L. The high potential connection 55 connects the other end 56 of the heater 84 with the lead L1.

The heaters 43 and 44, and the sections t5 and 63 may have the same wattage as given by way of example for corresponding heaters and sections of Figs. 1 to 4.

The thermostat may include a bulb 51, placed in the oven, and connected to a diaphragm 58, in the switch structure. The bulb 51 and diaphragm 58, together with the connecting tube 59 may be filled with a thermostatic liquid, such as to cause the diaphragm 58 to expand with a rise in temperature in the oven and to contract with a fall in temperature. A snap-acting mechanism 60, if desired, may be used, and is diagrammatically indicated by a rectangle and may be of any wellknown construction to cause the pusher 6| to snap the switch 62 into open and closed positions. The diaphragm 58 may be carried by internally threaded sleeve 53 which is axially free to move in the support 64; but is keyed against rotation by key 65. The internal threads of 63 cooperate with the external threads 68 on the shaft 61, So that rotation of the knob 40 counterclockwise moves the diaphragm 58 axially to the right, in Fig. 6, thus to adjust the diaphragm for the selected temperature setting, as is well-known. The movement of diaphragm 58, in the "0if position, may be sumciently far to the left, in Fig. 6, so that the diaphragm 58 cannot collapse sufliciently to close the switch 62, regardless of any temperature in the oven. This prevents energization of the heaters in the "off position.

The shaft 67 also rotates disks 68 and 69 which operate the switches 10 and H. The arm 12, in Fig. 5 is spring biased to the right, while the arm '73, in Fig. 5, is spring biased to the left. In the off position, the disks 68 and 69 allow the arms 82 and 13 to move, under sprin action, to open position, as illustrated in Fig. 5. The disk 69 is provided with a ridge it, which comes into contact with the arm 73 as the knob M is turned counterclockwise and closes the switch H, thus energizing the lower heater dd between the leads L and L1 throughout the baking temperature range of adjustment. In the baking range of adjustment, the disk 63 has no ridge, so that the switch 70 remains open, thus causing the upper heater 63 to be energized between the leads L and N, under a relatively low potential. Therefore, throughout the range of adjustment for bake conditions, the lower heater M is energized at maximum wattage and the upper heater 43 is energized at relatively lowwattage.

In the broil position of knob 40, the ridge 15, on the disk 68, reaches a position to move the arm 12 to the left, in Fig. 5, thus closing switch 10. At that time, the ridge M, on disk 69, is moved beyond contact with the arm 13, thus allowing the ridge H to close the switch H.

switch II to open. Under these conditions, the

section 45 of heater is energized between leads L and L1 while the section 46 isenergized between the leads Li and N. This energizesthe upper heater at its maximum wattage. The'lower heater N is deenergized in this broil position by the opening of switch H.

When it is desired to preheat, the knob 4|! is broil position, moves the arm 12 to close switch 10. This energizes a holding solenoid 16 across the lines L and Li and thus holds the switch closed as long as thermostatic switch B2 remains closed. Since the oven is below the selected temperature at this time, the switch 62 remains closed, so that after the knob is turned back to 400, the switches 62 and it remain closed. The turning of the knob 40 to 400 causes the Therefore, underthis preheat actuating, the heaters Al and M are energized at maximum wattage until the oven reaches the selected temperature of coo. At this time, the diaphragm W, acting throueh the snap-acting mechanisms 86, opens the switch 62 and deenergizes the solenoid. lii. This in turn opens the switch ill. As soon as the oven is cooled slightly, the switch 82 is again closed by the thermostatic diaphragm 58* but the solenoid i6 is not re-energiaed and the switch lil remains open. The heater 43 is therefore energised between the leads L and it at reduced wattage while the heater M is energized between the leads L and L1 at maximum wattage. The heaters will continue to he energized and cleenergizeol by the thermostat thereafter with the upper heater at reduced wattage and the lower heater at march mum wattage until the knob to is turned to the off or broil positions.

ii the user should desire to stop the use of a preheat cycle after having actuated the knob Kill for preheat, the knob Ml may he turned back to the oil position, thus opening the switch Bland cleenergiaing the holding coll E6. Thereafter the knob 50 may he turneclto any selected halie position without the use of the preheat circuit.

While I have shown a single pole thermostat controlling only the connections to lead L, it is to he understood that I may use a double pole thermostat to control the connections to both leads L and L1.

While the iorm of embodiment of the hlvention as herein disclosed, constitutes a preferred form, it is to he understood that other forms might be adopted, as may come within the scope of the claims which follow.

What is claimed is as follows:

1. In combination, an oven, on electrical upper heater in said oven, an electrical lower heater in said oven, two relatively high potential leads, a relatively low potential lead, said upper heater having one end and an intermediate top with high potential connections to said high potential leads respectively and its other end with a low potential connection to said low potential lead, said lower heater having its ends with high potential connections to said high potential leads respectively, an upper heater switch opening and. closing one of said high potential connections of said upper heater, 2. lower heater switch opening and closing one of said high potential connections of said lower heater, and another switch cooperatins with said switches to open all of said high potential connections in the "ofl condition.

2. In combination, an oven, an electrical upper heater in said oven, an electrical lower heater in said oven, two relatively high potential leads, a relatively low potential lead, said upper heater having one end and an intermediate tap with high potential connections to said high potential leads respectively and its other end with a low potential connection to said low potential lead, said lower heawr having its ends with high potential connections to said high potential leads respectively, and switch means having a plurality oi. cooking positions and an off condition and opening and closing one of said high potential connections or said upper heater in diilerent cooking positions, opening and closing one of said high potential connections of said lower heater in diiferent cookingpositions, and opening all of said high potential connections in the of! condition.

In combination, an oven, on electrical upper heater in said oven, an electrical lower heater in saiol oven, two relatively high potential leads, a relativelg low potential lead, said upper heater having one end and. an intermediate tan with high potential connections to said high potential leads respectively end its other end with a. low potential connection to said low potential lead, said. lower heater having its ends with high potential connections to said high potential leads respectively, and switch means having bake and broil positions and an o condition, and opening one of said potential connections of saiol upper heater in said bake position and closing said last named connection in said oroil position,

and opening one of said high potential connections of said lower heamr in said broil position and; closing saici last named connection in said halite position, anal opening all of saicl high potentiai connections the ofi condition.

5n combination, an oven, an electrical upper heater in said oven, on electrical lower heater in. saici oven, two relatively high potential leads, a relatively low potential lead, said upper heater having one end, and an intermediate top with high. potential connections to said high poten tial leacs respectively and it other end with a low potential connection to said low potential leaol, seicl lower heater having it ends with high potential connections to said high potential leads respectively, ancl switch means having preheat, hallo anal oroil positions and an 013" condition and opening one of said high potential connections oi. said upper heater in the bake position and closing saicl last named connection in the preheat and hroil positions, opening one of said high potential connections of said lower heater the hroil position and closing said last named connection in the preheat and bake positions and opening all of said high potential connections in the ofl condition.

5, In combination, an oven, on electrical upper heater in said oven, an electrical lower heater said oven, two relatively high potential leads, a relatively low potential lead, said upper heater having one engi and an intermediate tap with highpotential connections to said high potential leads respectively and its other end with a low potential connection to said low potential lead, said lower heater having its ends with high po tential connections to said high potential leads respectively, an upper heater switch opening and closing one of said high potential connections of said upper heater, a lower heater switch opening and closing one or said high potential oounections of aid lower heater, another switch cooperating with said switches to open all of said high potential connections in the of? condition, and thermostatic means cooperating with said switches to control the energization of said heaters in accordance with temperature conditions in said oven.

6. In combination, an oven, an electrical upper heater in said oven, an electrical lower heater in said oven, two relatively high potential leads, a relatively low potential lead, said upper heater having one end and an intermediate tap with high potential connections to said high potential leads respectively and its other end with a low potential connection to said low potential lead, said lower heater having its ends with high potential connections to said high potential leads respectively, an upper heater switch opening and closing one of said high potential connections of said upper heater, a lower heater switch opening and clming one of said high potential connections of said lower heater, another switch coopcrating with said switches to open all of said high potential connections inthe ofi condition, and thermostatic means opening and closing one of said switches in response to oven temperatures to maintain a predetermined temperature in said oven.

7. In combination, an oven, an electrical upper heater in said oven, an electrical lower heater in said oven, two relatively high potential leads, a

relatively low potential lead, said upper heater having one end and an intermediate tap with high potential connections to said high potential leads respectively and it other end with a low potential connection to said low potential lead, said lower heater having its ends with high potential connections to said high potential leads respectively, an upper heater switch opening and closing one of said high potential connections of said upper heater, a lower heater switch opening and closing one of said high potential connections or said lower heater, another switch cooperating with said switches to open all of said high potential connections in the "ofi" condition, thermo= static means cooperating with said switches to controlthe energization of said heaters in accordance with temperature conditions in said oven, temperature adjusting means for said thermostatic means, and a common manual actuator for said switches and adjusting means.

8. In combination, an oven, an electrical upper heater in said oven, an electrical lower heater in said oven, two relatively high potential leads, a relatively low potential lead, said upper heater aseaesc having one end'and an intermediate tap with high potential connections to said high potential leads respectively and its other end with a low potential connection to said low potential lead,

said lower heater having its ends with high potion, and opening one of said high potential connections of said lower heater in said broil position and closing said last named connection in said bake position, and opening all of said high potential connections in the .off condition, thermostatic means cooperating with said switch means to energize and deenergize said heaters in response to oven temperatures, temperature adjusting means for said thermostatic means, and a common manual actuator for said switch means and temperature adjusting means.

9. In combination, an oven, an electrical upper heater in said oven, an electrical lower heater in said oven, two relatively high potential leads, a relatively low potential lead, said upper heater having one end and an intermediate tap with high potential connections to said high potential leads respectively and its other end with a low potential connection to said low potential lead, said lower heater having its ends with high potential connections to said high potential leads respectively, switch means having preheat, bake and broil positions and an "o condition and opening one of said high potential connections of said upper heater in the bake position and closing said last named connection in the preheat and broil positions, opening one of said high potential connections of said lower heater in the broil position and closing said last named connection in the preheat and bake positions and opening all of said high potential connections in the oil condition, thermostatic means cooperating with said switch means to energize and deenergize said heaters in response to oven temperatures, temperature adjusting means for said thermostatic means, means controlled by said thermostatic means when said oven has been heated to a predetermined temperature while said heaters are energized in said preheat position for automatically changing said switch means from said preheat position to said bake position, and a common manual actuator for said switch means and temperature adjusting means.

MILLARD E. FRY. 

